1. Field of the Invention
The present invention relates to micro-particulate aluminosilicate synthesized in an aqueous solution and process of producing the micro-particulate aluminosilicate.
2. Description of Related Art
In general, it has been well known to artificially synthesize zeolite as an aluminosilicate by using a metal hydroxide or a metal salt, aluminate of a metal and colloidal silica. Nowadays, zeolite is finding a spreading use in various industrial fields because of its useful functions and characteristics such as ion exchanging of metal ions, sieving of molecules, adsorption of gases such as carbon dioxide, nitrogen oxide and sulfur oxide, reactive catalytic action, and so forth. Although natural zeolite is available, proportion of artificially synthesized zeolite is increasing because of large impurity content and lack of uniformity of particle size of natural zeolite.
As one of process for synthesizing zeolite, it has been attempted to bring a metal hydroxide or a metal salt, aluminate of a metal and colloidal silica into reaction in an aqueous solution. This process does not necessitate any specific equipment because it relies upon a simple mechanism of reaction conducted in an aqueous solution and, therefore, has been widely adopted as a synthesizing process for an artificial mass-production of zeolite at a low cost.
In recent years, there is an increasing demand for artificial production of designed aluminosilicate particles, e.g., uniformalization of particle size, refining of particles, increase in the purity and polygonal particle configuration approximating a spherical in place of conventional cubic or rectangular form of particles, in order to cope with current requirements for enhancement of ion-exchanging ability, ion-exchanging speed, absorbability and adsorption speed. This synthesis process for producing aluminosilicate in an aqueous solution, however, suffers from the following disadvantages. Namely, speed of growth of crystals after generation of crystal nucleus is high because of low viscosity of solvent, so that the mean particle size in terms of particle size distribution measured by precipitation method is as large as 6 .mu.m. In addition, the particle sizes are distributed over a wide range. Thus, the above-described process could not provide ultra-fine aluminosilicate particles of a mean particle size not greater than 4 .mu.m and having a narrow range of particle size distribution.